let ele_mount

function initMainBar() {

    let main_bar = document.querySelector("#main-bar")
    main_bar.innerHTML = `
        <ul>
 
        </ul>
    `
    ele_mount = main_bar.firstElementChild
    console.log(ele_mount)
}

/**
 *
 * @returns {*} 返回值为挂载的ul
 */
function getMainBarMount(){
    let li = document.createElement("li")
    li.className = 'bar-item'
    ele_mount.append(li)
    return li
}